The viscosity and adhesive strength of casein from the milk of 6 individual cows were determined on samples collected regularly over a period of 21 months. Three of the cows calved in autumn and 3 in spring. The viscosity of the casein from 5 of the cows showed a decline during lactation that was independent of the date of calving. It was therefore concluded that the decline in casein viscosity may be attributed to lactational rather than seasonal effects.

An experimental non-return valve was fitted in the short milk tube so that flow was permitted only in one direction, away from the teat. Liner movement was minimal because no air admission to the liner above the valve was provided. The extent of liner opening therefore depended on the amount of milk extracted within a pulsation cycle and on any air leakage past the liner mouthpiece. Milking experiments using four cows showed that the mean vacuum level in nominally open liners of valved teatcups during peak milk flow was 8·6 kPa higher than in conventional teatcups. Bench tests showed that the increase in liner vacuum (LV) depended on the nominal plant vacuum level, the pressure difference between initial LV and maximum pulsation chamber vacuum, the liner elasticity and mounting tension. The main source of energy available to raise LV above the nominal plant vacuum is the release of strain energy, stored within the liner during the collapse phase of each pulsation cycle.

Laboratory somatic cell count (LSCC) records are usually recorded monthly and provide an important information source for breeding and herd management. Daily milk viscosity detection in composite milking (expressed as drain time) with an automated on-line California Mastitis Test (CMT) could serve immediately as an early predictor of udder diseases and might be used as a selection criterion to improve udder health. The aim of the present study was to clarify the relationship between the well-established LSCS and the new trait,‘drain time’, and to estimate their correlations to important production traits. Data were recorded on the dairy research farm Karkendamm in Germany. Viscosity sensors were installed on every fourth milking stall in the rotary parlour to measure daily drain time records. Weekly LSCC and milk composition data were available. Two data sets were created containing records of 187 692 milkings from 320 cows (D1) and 25 887 drain time records from 311 cows (D2). Different fixed effect models, describing the log-transformed drain time (logDT), were fitted to achieve applicable models for further analysis. Lactation curves were modelled with standard parametric functions (Ali and Schaeffer, Legendre polynomials of second and third degree) of days in milk (DIM). Random regression models were further applied to estimate the correlations between cow effects between logDT and LSCS with further important production traits. LogDT and LSCS were strongest correlated in mid-lactation (r = 0·78). Correlations between logDT and production traits were low to medium. Highest correlations were reached in late lactation between logDT and milk yield (r = −0·31), between logDT and protein content (r = 0·30) and in early as well as in late lactation between logDT and lactose content (r = −0·28). The results of the present study show that the drain time could be used as a new trait for daily mastitis control.

α-Lactalbumin (α-La) is a protein found in the milk of all mammalian species and is involved in lactose biosynthesis in association with galactosyltransferase (Brodbeck et al. 1967). The primary structure of α-La from several species such as bovine (Brew et al. 1970), human (Findlay & Brew, 1972), and goat (McGillivray et al. 1979) has been determined. Hall et al. (1982) have established the nucleotide sequence and the organization of the human α-La gene (Hall et al. 1987).

This research communication reports concentrations of two sialic acids (SA), N-acetylneuraminic (Neu5Ac) and N-glycolylneuraminic (Neu5Gc), in fresh milk from different cow breeds throughout lactation. According to published studies, the two SA types found in animal-derived products have diverse and conflicting effects on human health, but SA content is not routinely analysed in individual milk cows samples. We measured the content of Neu5Ac and Neu5Gc in milk from Holstein Friesian (HO), Simmental (SM), Simmental × Holstein crossbred (SM×HO), and Podolica (POD) cows at 60 and 120 d following calving. HO, SM and SM×HO were reared in an intensive production while POD were raised in an extensive system. Results showed that total Neu5Ac was overall thirty times more abundant than Neu5Gc, and their concentrations were higher at 120 d than at 60 d (P < 0.001). Neu5Gc values were greater in HO, SM, and SM × HO than in POD (P < 0.001), while HO had a higher Neu5Ac value than the other three breeds (P < 0.001). These findings shed light on the differences in SA content among cow breeds and lay the groundwork for future research to select animals that produce milk with desirable characteristics for human health.

The aim of this work was to use X-ray diffraction to identify substances used for adulteration of raw milk and to determine if crystallographic analysis can detect extraneous substances in milk. Two unknown substances were sent anonymously by employers linked to the dairy chain, who claimed that they were added directly in milk prior to water addition by truck drivers. The samples were analyzed by X-ray diffraction and submitted to physicochemical analysis. The first substance was identified by X-ray diffraction as sodium citrate, complying with its physicochemical attributes, such as the powerful ability to decrease the freezing point. The second substance was identified by X-ray diffraction as sucrose and this result was also in agreement with its ability to increase the density, decrease the freezing point and finally, to be positive for sucrose in the resorcinol qualitative test. To evaluate if X-ray diffraction can detect extraneous substances already mixed in milk, fresh raw milk samples tampered with urea, sodium hydroxide, sodium citrate and sucrose were freeze dried and analyzed by X-ray diffraction, with no detection of any extraneous substances at any percentage. This is the first report of attempted diagnosis of extraneous substances in milk by X-ray diffraction. However, this technique can be useful only when applied to identify substances used for adulteration prior to its dilution in milk, since the amorphous nature of milk seems to be a limitation for the accurate detection of extraneous substances.

This research communication reports the results from questionnaires used to identify the impact of recent research into the disinfection of cattle foot-trimming equipment to prevent bovine digital dermatitis (BDD) transmission on (a) biosecurity knowledge and (b) hygiene practice of foot health professionals. An initial questionnaire found that more than half of participating farmers, veterinary surgeons and commercial foot-trimmers were not considering hand or hoof-knife hygiene in their working practices. The following year, after the release of a foot-trimming hygiene protocol and a comprehensive knowledge exchange programme by the University of Liverpool, a second survey showed 35/80 (43.8%) farmers, veterinary surgeons and commercial foot-trimmers sampled considered they were now more aware of the risk of spreading BDD during foot- trimming. Furthermore, 36/80 (45.0%) had enhanced their hygiene practice in the last year, impacting an estimated 1383 farms and 5130 cows trimmed each week. Participants who reported having seen both the foot-trimming hygiene protocol we developed with AHDB Dairy and other articles about foot-trimming hygiene in the farming and veterinary press, were significantly more likely to have changed their working practices. Difficulties accessing water and cleaning facilities on farms were identified as the greatest barrier to improving biosecurity practices. Participants' preferred priority for future research was continued collection of evidence for the importance and efficacy of good foot-trimming hygiene practices.

Figures showing the means and the standard deviation of butterfat percentage of milk samples, at the afternoon and morning milkings res-pectively, during the four quarters of the year are presented.

The probable sources of error due to the nature of the sample are discussed and the seasonal variability of mean and of standard deviation is considered.The likelihood of the mean of afternoon or of morning milk failing to reach certain specified minima during the respective seasons is calculated.

By the application of different water-soluble organic compounds and some protein-denaturing reagents dissolved therein, several stages in the dispersion of milk powder particles can be distinguished. The particles first swell, and agglomeration or coalescence follows. However, no dispersion necessarily takes place at this stage, as indicated by the absence of casein micelles in the surrounding liquid. In the initial stage of self-dispersion, ‘dispersion streams’ emanating from the powder particles may be observed. In certain cases, particularly with spray dried skim-milk, thin membranes may be perceived around the swollen and dispersing powder particles. The dispersibility is dependent upon the fat content of the powder and the method of manufacture.

With propylene glycol and butylene glycol no dispersion of powder particles took place. However, the hydrogen-bond breaking reagents, urea, guanidine hydrochloride and sodium salicylate, as well as an anionic detergent, sodium dodecyl sulphate dissolved in propylene glycol, caused dispersion of powder particles, particularly in spray dried powders. The limited dispersibility of roller dried powders in water could be greatly enhanced by the same reagents.

With water-insoluble liquids enough moisture penetrated through the medium to cause the crystallization of lactose in powder particles.

Large-scale manufacture of washed curd cheese has not yet been attempted in Britain. There seems to be no obvious obstacle, and the production of a good washed curd cheese would satisfy several present-day requirements. It is popular with consumers and would be an alternative to the usual standard varieties; it has certain economic advantages in manufacture and excellent properties for retail sale. In addition, low acid whey is in considerable demand as an important ingredient of certain proprietary brands of infant foods; such whey is not readily obtainable by normal cheese-making, but is produced during the manufacture of this cheese.

An artificial teat containing a force transducer was constructed to study the forces exerted by the liner on the teat during milking. The objective was to develop a method of comparing the action of different liners under a variety of different milking conditions. The rigid structure of the artificial teat did not provide an accurate representation of a real teat but deformable models used in the past have not proved practical. Initial tests of the teat showed that it gave repeatable results during calibration. When placed in a liner, however, repeatable results could not be obtained if the teat–liner interface was disturbed. The forces that were measured under simulated milking conditions varied with liner wall position and with time. There was a peak and trough prior to a stable asymptotie value being attained and a noticeable time lag behind pulsation chamber pressure. This technique can be used to compare liners when a reliable method of locating the artificial teat within the liner has been developed.

The effect of Staphylococcus aureus on detachment of bovine mammary epithelial cells in culture was examined. Mammary epithelial cells became detached from fresh monolayers following a 3 h incubation in the presence of Staph. aureus M60. Two different procedures indicated that cell detachment coincided with the S-phase of the cell cycle. The roles of proteinases, toxins and Ca availability in inducing cell detachment were examined. Addition of the proteinase inhibitor phenyl-methylsulphonyl fluoride (1 mM) to the culture medium prevented cell detachment. Addition of a combination of purified staphylococcal proteinases XVI and XVII-B to the culture medium of mammary epithelial cells induced cell detachment in the absence of Staph. aureus. Cell detachment may be caused by a staphylococcal proteinase. However, addition of Ca (10 mM) to the culture medium abolished Staph. aureus-induced cell detachment, despite the fact that proteinase activity was still apparently present. Isogenic mutants of Staph. aureus M60, expressing either ± or β toxins but not both, induced cell detachment, but to a lesser extent than the wild type. Thus, Ca and toxins play some role during cell detachment. Clones established from detached cells that were washed and replated showed the same susceptibility to Staph. aureus-induced cell detachment as the parental cells. This indicated that there is no subclone of mammary epithelial cells more sensitive to this effect.

1. Although chemical analysis, bacteriological analysis and graders' reports failed to distinguish the alcohol-glycerol rennet cheese from the brine rennet cheese, the marked qualities in body and texture during making of the alcohol-glycerol rennet curd, and the sterility or low count of the alcoholglycerol extract warrant further trials under practical conditions.

2. Where brine rennet may be suspected as the cause of bacterial faults, the alcohol-glycerol rennet could well be used in its place.

3. Alcohol-glycerolrennets have superior keeping-qualities to brine rennets.

The use of starter cultures prepared 3 days, 2 days and 1 day before inoculation at the 1% level into cold cream in the making of sweet cream starter butter was investigated. With Streptococcus diacetilactis starter there was little effect of age of starter on diacetyl production in the cream and on the quality of the fresh butter, but when 3-day-old culture was used in the cream there was a slight reduction in the butter quality after 4 and 8 months' storage. With the mixed commercial cultures Camb and F.D. increase in age of the culture led to reductions in diacetyl production in the cream. The difference was attributed to the effect of holding for the longer time under acid conditions on the equilibrium between streptococci and leuconostocs in the mixed culture. The age of the Camb culture had no effect on the grade of the butter, but holding the F.D. culture for 3 and 2 days instead of for 1 day caused a fall in grade of the butter after storage for 4 and 8 months at 14 °F.

1. The application of the colorimetric dilution method for the determination of pH values in cheesemaking is discussed and the necessary precautions for accuracy described.

2. Bromthymol blue is recommended for milk and whey of pH. > 5·8 and the B.D.H. 4460 indicator for whey of pH < 5·8.

3. Titratable acidities and pH values each afford an incomplete picture of the working of a curd. Together they afford a valuable indication of the normality or otherwise of the making process.

4. The buffer value of whey rises steadily during manufacture. The pH rises abruptly after salting, although the titratable acidity continues to increase.

5. The buffer value of whey is controlled chiefly by the rate of working but tends to be lower with pasteurized milk.

6. A diagrammatic method for summarizing the “behaviour of a vat” and for detecting abnormal working is described.